Question

package com.example.**.beatle.app;

import android.app.Fragment;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class MainActivity extends FragmentActivity   {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if(savedInstanceState==null)
    {
        getSupportFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}

public static class PlaceholderFragment extends Fragment {

    private ArrayAdapter<String> mForecastAdapter;


    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        String[] forecastArray = {"Today-Sunny-88/63", "Tommorrow-windy-88/94", "wed-aloo-alooo"};
        List<String> weekForecast = new ArrayList<String>(Arrays.asList(forecastArray));
        mForecastAdapter = new ArrayAdapter<String>(getActivity(), R.layout.fragment_main, R.id.list_item_forecast_textview, weekForecast);
        ListView listView = (ListView) rootView.findViewById(R.id.list_view_forecast);
        listView.setAdapter(mForecastAdapter);
        return rootView;

    }
}}

消息Gradle Build 错误：（27,59）错误：找不到合适的add方法（int，PlaceholderFragment）方法FragmentTransaction.add（Fragment，String）不适用（参数不匹配; int无法转换为Fragment）方法FragmentTransaction.add（int，Fragment）不适用（参数不匹配; PlaceholderFragment无法转换为Fragment）注意：某些消息已经简化;使用-Xdiags重新编译：详细以获得完整输出错误：任务'：app：compileDebugJava'的执行失败。编译失败;有关详细信息，请参阅编译器错误输出。

Answer 1

您正在使用FragmentActivity和getSupportFragmentManager()。因此，PlaceholderFragment需要继承android.support.v4.app.Fragment，而不是android.app.Fragment。

Answer 2

使用

 import android.support.v4.app.Fragment;

而不是

import android.app.Fragment;

项目全部。

另外，使用FragmentManager和FragmentTransaction的支持库。

Answer 3

如果您使用Andorid Jetpack的 AndroidX ，请使用

androidx.fragment.app.Fragment

而不是

import android.app.Fragment;
// or
import android.support.v4.app.Fragment;

无法解析方法'add（int，com.example。**。beatle.app.MainActivity.PlaceholderFragment）

3 个答案: